Spontaneous intracranial hypotension: the headache that eases when lying down

The brain and spinal cord are surrounded by cerebrospinal fluid (CSF) held within a membrane called the dura. If the dura leaks, usually in the spine, the fluid volume falls and the brain loses some of its buoyancy and support. The Cardiff journal club review explains that the leak is commonly near the spinal nerve roots, and that risk factors include connective tissue disorders, bariatric surgery and spinal pathologies such as osteophytes and disc prolapse.

Another review recognises three types of CSF leak: a ventral leak from a dural tear secondary to a calcified disc herniation or an osteophyte, leaking meningeal diverticula, and CSF-venous fistula. It also notes a possible association with genetic connective tissue disorders such as hypermobile Ehlers-Danlos syndrome and Marfan syndrome, although the evidence from prospective studies is mixed.

A systematic review of more than 2,000 cases, summarised in the Cardiff journal club, found headache in 97% of patients, usually orthostatic (92%) and most often occipital, frontal or diffuse. Associated symptoms included nausea or vomiting (54%), neck pain or stiffness (43%), hearing disturbances (28%) and dizziness (27%). Mean age at onset was 42.5 years, with a wide range, and females were affected twice as often.

Not everyone has the classic pattern. The second review notes that orthostatic headache is often, although sometimes erroneously, deemed synonymous with SIH, and the journal club describes a case series of CSF-venous fistula where the headache was often made worse by the Valsalva manoeuvre, with only 69% describing an orthostatic component. Rarely, the sagging of the brain can cause a syndrome of personality change, apathy and cognitive impairment that mimics behavioural variant frontotemporal dementia, which in the case series reversed on treating the leak.

• A headache that is worse within minutes of sitting or standing and eases lying flat, often at the back of the head.

• Nausea, neck stiffness, muffled hearing or ringing in the ears, dizziness.

• Headache that is worse with coughing or straining.

• Some people have atypical patterns, for example a headache that is made worse by straining rather than by posture.

A sudden, severe, thunderclap headache, a headache with weakness, confusion, fits or loss of consciousness, a stiff neck with fever or a rash, or a headache after a head injury needs emergency assessment: call 999 or go to A&E. An orthostatic headache that is new, persists for days or follows a spinal procedure should be assessed by a GP promptly, who may refer to neurology.

Diagnosis combines the history with brain MRI with contrast and sometimes spinal imaging. The systematic review found diffuse pachymeningeal (dural) enhancement in 73%, venous engorgement in 57%, brain sagging in 43% and subdural collections in 35%, while 19% had a normal brain MRI. Extradural CSF was detected on spinal imaging in 48% to 76%, but the exact leak site was often difficult to locate; digital subtraction myelography was most successful, with leaks most commonly in the thoracic spine.

Lumbar puncture is not always needed. The journal club's comment is that in most cases orthostatic headache and brain MRI findings are diagnostic, that lumbar puncture can show low pressure but is often not required diagnostically and may worsen symptoms, and that 32% of cases that had a puncture had normal opening pressure. In CSF-venous fistula the brain MRI is abnormal in over 80% but the opening pressure is commonly normal, and the fistula requires specialised myelography to find.

Treatment is stepwise. The second review lists conservative management (bed rest, analgesics, hydration and caffeine), epidural patching with the person's own blood or fibrin, surgical repair and endovascular procedures. It notes that some spinal CSF leaks are self-limiting and that people are usually advised to try a short period of conservative management, but that conservative management alone is estimated by meta-analysis to be enough in 28%. Oral caffeine is often recommended, although the review notes there are no controlled studies of caffeine in SIH.

If conservative measures fail, an epidural blood patch is the first-line interventional treatment. In the systematic review it was successful in 64% of cases, with larger volumes (over 20 ml) more effective than smaller (77% versus 66%) and no significant difference between targeted and non-targeted patches. The second review advises not delaying blood patches while conservative treatments are tried. For CSF-venous fistula, patches were far less effective (a good response in only 10% lasting 3 months) but surgery led to improvement in over 80% and headache freedom in nearly half.

Many people recover fully, but diagnosis can take months or years because of how often it is mistaken for migraine, tension headache or other conditions. The reviews describe the evidence base as limited because of the rarity of the condition, with mostly retrospective studies and no universally accepted definition. After surgery for a CSF-venous fistula, transient rebound intracranial hypertension (raised pressure) occurred in 7% in one series, and leaks can be hard to locate, so follow-up with neurology matters.

Keeping a headache diary that records posture and timing can help your doctor. If you have a known connective tissue disorder, tell clinicians because the reviews note a possible association.

On the NHS, assessment is usually by neurology with MRI, and blood patches are done by anaesthetics or pain services, with specialist spinal imaging and surgery concentrated in a small number of centres. Awareness among non-specialists is limited, so it can help to name the possibility explicitly.

A private neurologist may arrange imaging more quickly, but complex leak localisation and surgery usually involve a specialist centre. Ask clearly how treatment decisions and follow-up will be coordinated.